1. Field of Invention
The present invention relates to an inkjet print technology, and more particularly to a circuit of a multiplexing inkjet print system and a control circuit thereof.
2. Related Art
Along with the progress of science and technology, inkjet print technology tends to develop an inkjet chip having high resolution, high print speed, and a large number of jet orifices, so as to achieve the application in more sophisticated fields. Ink drop of smaller size can achieve a higher print resolution. However, under the same conditions, if the resolution is improved, the print speed is lowered. Thus, in order to improve the print speed and the print resolution in sync, the most effective way is to increase the number of the jet orifices on a single inkjet chip.
In the circumstance of thermal inkjet printing, each ink drop generator is actuated by controlling the current passing through a resistance element. Here, the resistance element generates heat in response to the current, thereby heating the ink in a vaporizing cavity nearby the resistance element, so as to boil the ink to generate steam bubbles. As the steam bubbles expand, the ink is pushed toward the jet orifices and forms droplets at the top end of the jet orifices. When the steam bubbles keep expanding, the droplets may get rid of the surface tension of the ink under the pressure of the steam bubbles and then are spurted out through the jet orifices.
As for a conventional inkjet printhead with a small number of jet orifices, the operating state of a heating resistor is determined by the on/off of the external contacts. When such as a switching element of a field-effect transistor (FET) is driven by a gate, the current passes through the heating resistor, making the heating resistor generate heat to heat the ink, thus spurting ink out through the jet orifices. However, in this one-to-one driving manner, when the number of the required jet orifices increases, the number of the external contacts increase correspondingly, such that the manufacturing cost of the printhead and print device raises and the fabricating and assembling thereof also become more difficult.
Therefore, a two-dimensional matrix driving manner is developed, in which a plurality of address lines forms the first dimension and a plurality of power lines forms the second dimension, such that the number of the jet orifices is the product of the number of the address lines and the number of the power lines. One end of the heating resistor is electrically connected to a power line and the other end thereof is electrically connected to the drain of an FET. Moreover, the source of the FET is electrically connected to ground and the gate thereof is electrically connected to the address line. Only when the address line corresponding to the heating resistor turns on the FET connected thereto and the power line electrically connected thereto provides a proper voltage or current, the heating resistor starts operating, as shown in U.S. Pat. No. 5,635,968. As for an inkjet printhead adopting the two-dimensional matrix driving manner, generally 200˜300 jet orifices are provided, and when more jet orifices are required, the number of the external contacts may also increase.
Thus, in order to satisfy the requirement of 400 or more jet orifices, a three-dimensional matrix driving manner is developed to greatly increase the number of the jet orifices without greatly increasing the number of the external contacts.
Here, the three-dimensional matrix driving manner is achieved by adding a select line to the two-dimensional matrix driving architecture constituted by an address line and a power line. Referring to FIG. 1, in each of the heater circuits, one end of the heating resistor R is electrically connected to a power line and the other end thereof is electrically connected to the drain of a first FET M1. The source of the first FET M1 is electrically connected to ground and the gate thereof is electrically connected to the source of a second FET M2. The drain and gate of the second FET M2 are respectively electrically connected to an address line LA and a select line LQ. When the address line LA and select line LQ are both at a high electric potential, the first FET M1 is turned on and meanwhile the power line LP also provides a proper voltage or current. At this time, the heating resistor R starts operating. Here, the number of the jet orifices is the product of the number of the select lines, the number of the address lines, and the number of the power lines, as shown in U.S. Pat. No. 6,176,569 and U.S. Pat. No. 6,431,677.
As for another similar architecture adopting a three-dimensional matrix driving manner, referring to FIG. 2, effective lines LE constitute the third dimension, and the number of the jet orifices is the product of the number of the effective lines LE, the number of the address lines LA, and the number of the power lines LP, as shown in U.S. Pat. No. 6,402,279. In practice, the above-mentioned architecture may form 37 electric contacts for the printhead when 416 jet orifices are provided.
The above three-dimensional matrix driving manner still has limitations, i.e., though the increase of the number of the select lines or effective lines that constitute the third dimension may reduce the electric contacts between the printhead and the host, the heater circuit becomes more complicated. That is, in addition to using the two FETs to control the operating state of the heating resistor, more FETs (such as FETs M3, M4, M5 in FIG. 1 and FET M6 in FIG. 2) are required to provide the discharge function, so that the first FET may not be turned on by noises or unexpected coupling voltage, thereby avoiding operation mistakes when the heating resistor stops working.
In order to further increase the jet orifices and reduce the electric contacts, a manner of sequence input is adopted to provide 640 jet orifices, which requires only 26 electric contacts to the host. The architecture of the related driving circuit can refer to U.S. Pat. No. 6,312,079. However, such a data input manner requires a fast semiconductor device to process a huge amount of sequence input data. Moreover, high-pressure drive is required to provide energy for ink jet, so the problems such as high power consumption, complicated process, and high cost still exist.
In another three-dimensional matrix driving manner, the power line LP, address line LA, and address start line LD constitute the drive of three-dimensional matrix. Referring to FIG. 3, in each of the heater circuits, the heating resistor R is disposed between the power line LP and the drain of a power transistor M7. The address line LA and the address start line LD are electrically connected to the gate of the power transistor M7 through a logic element. When the address line LA and address start line LD are both of logic low signal “0”, the logic high signal “1” is generated after the operation of the logic element, so as to turn on the power transistor M7. Meanwhile, the power line LP also provides a proper voltage or current, and then the heating resistor R starts operating. Meanwhile, the heating resistors R connected to the same power line LP are turned on in sync to accelerate printing rate. However, the printhead control circuit is constituted of decoders, and image data is designated to the corresponding jet orifices after being decoded by the decoders, so plenty of control signal input is required.
Although in the conventional art, several three-dimensional matrix driving manners are provided to accelerate printing rate and improving the print resolution in sync, and to greatly increase the jet orifices without greatly increasing the number of the external contacts, the aforementioned three-dimensional matrix driving manners have limitations, such as complicated circuit structure, high power consumption, high cost, the increase of the contacts for the control signals. Moreover, along with the progress of science and technology, the number of the jet orifices provided by the conventional art under an acceptable number of electric contacts will not satisfy the requirements. Therefore, in order to improve the print speed and print resolution at the same time, it remains a subject for the relevant researchers to increase the number of the jet orifices in a single inkjet chip without greatly increasing the number of the external contacts and meanwhile avoiding increasing the power consumption, circuit complexity, and area.